.\" mtx.1  Document copyright 2000 Eric Lee Green
.\"  Program Copyright 1996, 1997 Leonard Zubkoff
.\"  Copyright 2007-2008 by Robert Nelson <robertn@the-nelsons.org>
.\"  Extensive changes 2000 by Eric Lee Green <eric@badtux.org>
.\"
.\" This is free documentation; you can redistribute it and/or
.\" modify it under the terms of the GNU General Public License as
.\" published by the Free Software Foundation; either version 2 of
.\" the License, or (at your option) any later version.
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.\" and "executables" are to be interpreted as the output of any
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.\" This manual is distributed in the hope that it will be useful,
.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
.\" GNU General Public License for more details.
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.\" You should have received a copy of the GNU General Public
.\" License along with this manual; if not, write to the Free
.\" Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139,
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.\"
.TH MTX 1 MTX1.3
.SH NAME
mtx \- control SCSI media changer devices 
.SH SYNOPSIS
mtx [-f <scsi-generic-device>] [nobarcode] [invert] [noattach] command [ command ... ]
.SH DESCRIPTION
The 
.B mtx
command controls single or multi-drive SCSI media changers such as
tape changers, autoloaders, tape libraries, or optical media jukeboxes.
It can also be used with media changers that use the 'ATTACHED' API, 
presuming that they properly report the MChanger bit as required
by the SCSI T-10 SMC specification. 
.SH OPTIONS
The first argument, given following
.B -f
, is the SCSI generic device corresponding to your media changer. 
Consult your operating system's documentation for more information (for
example, under Linux these are generally /dev/sg0 through /dev/sg15, 
under FreeBSD these are /dev/pass0 through /dev/passX,
under SunOS it may be a file under /dev/rdsk).  
.P
The 'invert' option will invert (flip) the media (for optical jukeboxes that
allow such) before inserting it into the drive or returning it to the
storage slot. 
.P
The 'noattach' option forces the regular media changer API even if the
media changer incorrectly reported that it uses the 'ATTACHED' API. 
.P
The 'nobarcode' option forces the loader to not request barcodes even if
the loader is capable of reporting them.  
.P
Following these options there may follow
one or more robotics control
commands. Note that the 'invert' and 'noattach'
options apply to ALL of robotics control
commands.

.SH COMMANDS
.TP 10
.B --version
Report the mtx version number (e.g. mtx 1.2.8) and exit. 

.TP 10
.B inquiry
Report the product type (Medium Changer, Tape Drive, etc.), Vendor ID,
Product ID, Revision, and whether this uses the Attached Changer API
(some tape drives use this rather than reporting a Medium Changer on a
separate LUN or SCSI address). 
.TP 10
.B noattach
Make further commands use the regular media changer API rather than the 
_ATTACHED API, no matter what the "Attached" bit said in the Inquiry info.
Needed with some brain-dead changers that report Attached bit but don't respond
to _ATTACHED API. 
.TP 10
.B inventory
Makes the robot arm go and check what elements are in the slots. This
is needed for a few libraries like the Breece Hill ones that do not 
automatically check the tape inventory at system startup. 
.TP 10
.B status
Reports how many drives and storage elements are contained in the
device. For each drive, reports whether it has media loaded in it, and
if so, from which storage slot the media originated. For each storage
slot, reports whether it is empty or full, and if the media changer
has a bar code, MIC reader, or some other way of uniquely identifying
media without loading it into a drive, this reports the volume tag
and/or alternate volume tag for each piece of media.
For historical reasons drives are numbered from 0 and storage slots are
numbered from 1. 
.TP 10
.B load <slotnum> [ <drivenum> ]
Load media from slot <slotnum> into drive <drivenum>. Drive 0 is assumed
if the drive number is omitted.
.TP 10
.B unload [<slotnum>] [ <drivenum> ]
Unloads media from drive <drivenum> into slot <slotnum>. If <drivenum> is
omitted, defaults to drive 0 (as do all commands).
If <slotnum> is omitted, defaults to the slot
that the drive was loaded from. Note that there's currently no way to
say 'unload drive 1's media to the slot it came from', other than to 
explicitly use that slot number as the destination.
.TP 10
.B [eepos <operation>] transfer <slotnum> <slotnum>
Transfers media from one slot to another, assuming that your mechanism is
capable of doing so. Usually used to move media to/from an import/export
port. 'eepos' is used to extend/retract the import/export 
tray on certain mid-range to high end tape libraries (if, e.g., the tray was
slot 32, you might say say 'eepos 1 transfer 32 32' to extend the tray). 
Valid values for eepos <operation>
are 0 (do nothing to the import/export tray), 1, and 2 (what 1 and 2 do varies
depending upon the library, consult your library's SCSI-level 
documentation). 
.TP 10
.B [eepos <operation>] [invert] [invert2] exchange <slotnum> <slotnum> [<slotnum>]
Move medium from the first slot to the second slot, placing the medium
currently in the second slot either back into the first slot or into the
optional third slot. 

.TP 10
.B first  [<drivenum>]
Loads drive <drivenum> from the first slot in the media
changer. Unloads the drive if there is already media in it (note: you
may need to eject the tape using your OS's tape control commands
first).  Note that this command may not be what you want on large
tape libraries -- e.g. on Exabyte 220, the first slot is usually a
cleaning tape. If <drivenum> is omitted, defaults to first drive.
.TP 10
.B last [<drivenum>]
Loads drive <drivenum> from the last slot in the media changer. Unloads
the drive if there is already a tape in it. (Note: you may need to eject
the tape using your OS's tape control commands first).  
.TP 10
.B previous [<drivenum>]
Unloads the drive and loads the previous tape in sequence. If the drive
was empty, loads the first tape into the drive.
.TP 10
.B next [<drivenum>]
Unloads the drive and loads the next tape in sequence. If the drive was
empty, loads the first tape into the drive.
.TP 10
.B position <slotnum>
Positions the robot at a specific slot. Needed by some changers to
move to and open the import/export, or mailbox, slot.
.TP 10
.B eject
Eject the tape currently in the drive.

.SH AUTHORS
The original 'mtx' program was written by Leonard Zubkoff and extensively
revised for large multi-drive libraries with bar code readers 
by Eric Lee Green <eric@badtux.org>. See 'mtx.c' for other contributors. 
.SH BUGS AND LIMITATIONS
.P
You may need to do a 'mt offline' on the tape drive to eject the tape
before you can issue the 'mtx unload' command. The Exabyte EZ-17 and 220
in particular will happily sit there snapping the robot arm's claws around
thin air trying to grab a tape that's not there. 
.P
For some Linux distributions, you may need to re-compile the kernel to
scan SCSI LUN's in order to detect the media changer. Check /proc/scsi/scsi
to see what's going on. 
.P
If you try to unload a tape to its 'source' slot, and said slot is
full, it will instead put the tape into the first empty
slot. Unfortunately the list of empty slots is not updated between
commands on the command line, so if you try to unload another drive to
a full 'source' slot during the same invocation of 'mtx', it will try
to unload to the same (no longer empty) slot and will urp with a SCSI
error.
.P

This program reads the Mode Sense Element Address Assignment Page
(SCSI) and requests data on all available elements. For larger
libraries (more than a couple dozen elements)
this sets a big Allocation_Size in the SCSI command block for the
REQUEST_ELEMENT_STATUS command in order to be able to read the entire
result of a big tape library. Some operating systems may not be able
to handle this. Versions of Linux earlier than 2.2.6, in particular,
may fail this request due to inability to find contiguous pages of
memory for the SCSI transfer (later versions of Linux 'sg' device do
scatter-gather so that this should no longer be a problem).
.P
The 
.B eepos
command remains in effect for all further commands on a command
line. Thus you might want to follow 
.B eepos 1 transfer 32 32
with 
.B eepos 0
as
the next command (which clears the 
.B eepos
bits). 
.P
Need a better name for 'eepos' command! ('eepos' is the name of the bit
field in the actual low-level SCSI command, and has nothing to do with what
it does). 
.P

This program has only been tested on Linux with a limited number of
tape loaders (a dual-drive Exabyte 220 tape library, with bar-code
reader and 21 slots, an Exabyte EZ-17 7-slot autoloader, and a Seagate
DDS-4 autochanger with 6 slots). It may not work on other operating systems 
with larger libraries,
due to the big SCSI request size. 
Please see the projecdt page http://sourceforge.net/projects/mtx for information 
on reporting bugs, requesting features and the mailing list for peer support.
.SH HINTS
Under Linux, 
.B cat /proc/scsi/scsi
will tell you what SCSI devices you have.
You can then refer to them as 
.B /dev/sga,
.B /dev/sgb, 
etc. by the order they
are reported.
.P
Under FreeBSD, 
.B camcontrol devlist
will tell you what SCSI devices you
have, along with which 
.B pass
device controls them.
.P
Under Solaris, set up your 'sgen' driver so that it'll look for
tape changers (see /kernel/drv/sgen.conf and the sgen man page), type
.B touch /reconfigure
then reboot. You can find your changer in /devices by typing
.B /usr/sbin/devfsadm -C
to clean out no-longer-extant entries in your /devices directory, then
.B find /devices -name \e\(**changer -print
to find the device name. Set the symbolic link 
.B /dev/changer 
to point
to that device name (if it is not doing so already).
.P
With BRU, set your mount and unmount commands as described on the BRU
web site at http://www.bru.com to move to the next tape when backing up
or restoring. With GNU 
.B tar,
see 
.B mtx.doc
for an example of how to use
.B tar
and 
.B mtx
to make multi-tape backups. 

.SH AVAILABILITY
This version of 
.B mtx
is currently being maintained by Robert Nelson <robertnelson@users.sourceforge.net> .
The 'mtx' home page is http://mtx.sourceforge.net and the actual code is currently available
there and via SVN from http://sourceforge.net/projects/mtx. 
.SH SEE ALSO
.BR mt (1), loaderinfo (1), tapeinfo (1), scsitape (1), scsieject (1)
